Page 195 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

I76 w Chapter fifteen

FLASH
Yet another technology called FLASH is generally regarded as an evolu-
tionary step that combines the best features from EPROM and E2PROM.
The name FLASH is derived from its fast reprogramming time compared to
EPROM. FLASH has been under development since the end of the 1970s, and
was officially described in 1985, but the technology did not initially receive a
great deal of interest. Towards the end of the 1980s, however, the demand for
portable computer and communication systems increased dramatically, and
FLASH began to attract the attention of designers.
All variants of FLASH are electrically erasable like E2PROMs. Some
devices are based on a single transistor cell, which provides a greater capacity
than an E2PROM, but which must be erased and reprogrammed on a device-
wide basis similar to an EPROM.
Other devices are based on a dual
transistor cell and can be erased and
reprogrammed on a word-by-word
basis (see Chapter 16 for more
details).
FLASH is considered to be of
particular value when the designer
requires the ability to reprogram a
system in the field or via a communi-
cations link while the devices remain
resident on the circuit board.

MRAMs
A technology that is attracting a great deal of interest for the future is
magnetic random access memory (MRAM),20 which may be able to store more
data, read and write data faster, and use less power than any of the current
memory technologies. In fact, the seeds of MRAM were laid as far back as
1974, when IBM developed a component called a magnetic tunnel junction
(MTJ), which comprises a sandwich of two ferromagnetic layers separated by a

20 In conversation, MRAM is pronounced “M-RAM.” That is, by spelling out the “M” and
following it with “RAM” to rhyme with “ham.”